Sang-wook Kwon

Tx Leakage Cancellers for 24 GHz and 77 GHz Vehicular Radar Applications

Tx leakage cancellers for 24 and 77 GHz vehicular radar systems are presented. These have high Tx-to-Rx isolation and wideband characteristics. Tx leakage cancellers are composed of four Lange couplers, a 90deg delay line, and a Wilkinson combiner. Tx leakage cancellers are implemented on GaAs substrate. A 24 GHz Tx leakage canceller shows the transmitting loss of 5.7 dB and Tx leakage cancellation of 28.1 dB. Also a 77 GHz Tx leakage canceller shows the transmitting loss of 3.6 dB and Tx leakage cancellation of 28.2 dB. Isolations due to Lange coupler are 15.1 dB in 24 GHz Tx leakage cancellers and 13.1 dB in 77 GHz Tx leakage cancellers, respectively. The isolations due to the topology of the Tx leakage canceller are expected to be 13 dB and 15.1 dB, respectively. These compact Tx leakage cancellers show wideband characteristics of bandwidth beyond 4 GHz

Force Coupled Electrostatic RF MEMS SP3T Switch

An electrostatic RF MEMS SP3T switch using an axial force coupling is proposed. Topologically equivalent three switching membranes are coupled through flexible beams so that the deflection of one switching membrane develops mutual axial load and moment to the others (one in already ON state and the other in idle state) and helps them easily be OFF. A built-in silicon stopper amplifies an axial force and moment by restricting the displacement of coupling beams. With maintaining a low driving stiffness, about 34 % increase in the restoring stiffness was examined by the simulation. Symmetric tri-layer film stack (sandwich like) is preferred to minimize the warpage of large membrane for low driving voltage. A RF characteristics of unit switch is measured to 0.25dB-insertion loss and 51.5 dB isolation at 2 GHz with 20 V r iving voltage. Especially high RF isolation over 45 dB is achieved even at 10 GHz by using the proposed force coupled driving concept. Switching time is measured to 7.5 mus for ON switching and 3.2 mus for OFF switching

Performance analysis of DRX mechanism considering analogue beamforming in millimeter-wave mobile broadband system

To meet the explosive growth of mobile traffic, it is necessary to guarantee high data rate in todays communication system. One of the methods to support high data rate is to use wide bandwidth (spectrum). Due to the limitation of frequency spectrum for the commercial usage, we choose millimeter-Wave (mmW) band of 30GHz and exploit analogue beamforming technique, focusing electro-magnetic wave energy at a certain direction, not an omni-direction. In the analogue beamforming technique, beam selection is required so that base station (BS) and mobile station (MS) communicate with the best beam each other and this procedure is performed periodically for the selected beams not to be mis-aligned. To extend battery lifetime of user equipment, current broadband system such as 3GPP LTE/LTE Advanced adopts discontinuous reception (DRX) which the new mmW system needs too. Therefore, we propose the DRX mechanism considering analogue beamforming technique and analyze the performance of the system varying parameters of beam selection and DRX according to the given beam pattern, traffic model and movement of MS.

Optimal positioning of repeater resonator for mid-range magnetic resonance wireless power link

Magnetic resonance wireless power link including a non-coaxially aligned repeater resonator has been analyzed and designed for efficient mid-range wireless powering. Parametric study on the power transfer efficiency (PTE) for several meter distance range indoor powering has been made and optimization condition for maximum PTE have been obtained. The results are expected to be utilized for mid-range wireless powering in the presence of practical limitations of the resonator location.

A novel resonator for robust lateral-misalignment of magnetic resonance wireless power link

A novel resonator structure for lateral-misalignment of wireless power transfer is presented. The proposed resonator is composed of a concentrated coil and several small loop coils. The uniform magnetic field distributions of the proposed resonator are described. The proposed hybrid resonator improves about 30% of the relative efficiency variation for a lateral-misalignment.

Thick membrane operated rf microelectromechanical system switch with low actuation voltage

Most researcher who have studied the radio frequency (rf) microelectromechanical system (MEMS) switch has focused on the electrostatic actuation types switch because of this type’s low power consumption, simple fabrication method, and good rf characteristics compared to magnetic, thermal, and piezoelectric driving method. However, most of electrostatic actuation type switch needs high operation voltage compared to other types. One of the reasons that affect the high operation voltage is the bending of the membrane because of an internal stress gradient. This bending increases the gap between electrode and membrane. To solve this problem, the authors developed the thick membrane operated seesaw type rf MEMS switch. This membrane consisted of a pivot under single crystal thick silicon membrane for a seesaw mode operation and a flexible spring for an up-down actuation mode. After the fabrication of this switch, the authors measured its rf characteristics. The minimum actuation voltage was about 12V, the isol...

Magnetic resonance wireless power transfer system for practical mid-range distance powering scenario references

Practical magnetic resonance wireless power transfer (WPT) system is presented. High-efficient power amplifier (PA) and adaptive tracking modules are combined with optimized wireless power links to propose mid-range wireless powering application scenarios in home-environments.

Wireless powering management by analog circuitry based in-band signaling controller

Efficient wireless charging control scheme for powering a single device unit is presented. The proposed scheme uses in-band communication and analog circuits to control the clock signal lengths. Since it can generate the control data packets without MCU, it is easy to implement a one-chip of the RX parts. We have verified the performance of the in-band communication for the WPT system while a mobile device is in charging.

Thick-membrane-operated radio frequency switches with wafer-level package using gold compressive bonding

An electrostatically actuated radio frequency (rf) switch is fabricated using a thick silicon membrane, and the device is packaged using a high resistivity silicon cap wafer with a gold (Au) thermocompressive bonding method. To achieve an rf switch that can operate at low voltage, a thick membrane with a pivot under the membrane is used. This design makes it possible to maintain the very small gap between the electrodes and the membrane without bending. A cavity with a pivot-patterned silicon wafer and a coplanar waveguide (CPW) signal-line-formed glass wafer is bonded using an anodic bonding method. After a mechanical polishing process, a deep reactive ion etcher is used to fabricate the membrane structure with a spring and a spring bar. To package the fabricated rf switch, an Au thermocompressive bonding process is used. A 1-µm-thick sputtered Au layer is used as intermediate bonding material. The bonding temperature and pressure are 350 °C and 63 MPa, respectively, and the time duration of the bonding is set to 30 min. The electrodes of the switch and the electrical contact pads on the cap wafers are interconnected via a hole and a sputtered Au metal layer. The total size of the complete packaged rf switch is 2.2 × 1.85 mm, and its rf characteristics have been measured using a Hewlett−Packard (HP) 8510C network analyzer. The measured driving voltage is approximately 16 V, the isolation is approximately −38.4 dB, and the insertion loss is approximately −0.43 dB at 2 GHz.